Reconstruction of the early dinosaur Herrerasaurus ischigualastensis from the Late Triassic (Carnian stage) Argentina. This genus was described by Osvaldo Reig back in 1963, but due to the fragmentary nature of the bones, the classification of the animal was controversial (opinions were expressed that it was a prosauropod or even a dinosaur outside the two main groups). Only in 1988 was a complete skeleton with a skull found, which allowed reconstructing the dinosaur and its approximate kinship. However, it is still unclear whether Herrerasaurus was an early theropod or whether it was closer to sauropodomorphs. The remains, named Ischisaurus cattoi and Frenguellisaurus ischigualastensis, were later assigned to Herrerasaurus.
Herrerasaurus is interesting for its rather large size for an early predatory dinosaur: some specimens of "Frenguellisaurus" reached 6 m. The skull was relatively small, but the jaws carried sharp saw-toothed teeth, including "fangs". There was also a shock-absorbing joint in the middle of the jaw, which allowed holding large prey. The hands were armed with three grasping fingers, and the longest of them was the third. The rudimentary fourth and fifth fingers were hidden by soft tissues. The pelvis of a Herrerasaurus is unusual. Only two sacral vertebrae fused with it (at least 3 in other dinosaurs), and the acetabulum was not completely open. At the same time, the pubic bone was directed not forward, but backward, as in maniraptorans, and carried a massive "boot". At one time, this served as the basis for Gregory Paul to designate the herrerasaurs as an early group in which bird-like features arose, and even to bring them closer to the "protoavis".
In this work, I tried out a style with shading using a black pencil, not a pen. It is much easier to apply shadows with a pencil, and I liked the result. It shows an extensive cover of filaments inspired by a possible "fluffy" ancestral state for ornithodirans (dinosaurs, pterosaurs and small groups close to them).
Black ballpoint pen and black colored pencils, 2023.